Mechanisms of tumor-related epileptogenesis remain poorly understood. In tumor-associated epilepsy, nontumoral surrounding tissue may cause seizures.39 Abnormal growth kinetics of tumors can affect surrounding neurons morphologically and biochemically, altering neuronal structure and affecting the release of neurotransmitters and neuromodulators such as gamma-aminobutyric acid (GABA) and somatostatin. These changes may cause seizures through hyperexcitability or reduced inhibition. 40,41
The hippocampus may become involved—either directly, through tumor extension, or indirectly, through increased excitatory input caused by a tumor—and may contribute to seizure amplification and propagation.42
Tumors can disrupt normal electrical functional patterns, causing increased local coherence, or similarity of electrical activity seen electrographically within a cortical region, which is a similar pattern observed in epileptic foci.43 These changes, induced by a tumor in the surrounding tissue, contribute to the formation of the epileptogenic zone.
Cortical connections contribute to generation and maintenance of seizures. Aggressive white-matter neoplasms are less likely to cause seizures because they do not directly irritate cortex, and tumor growth may disrupt the spread of epileptic activity.17
Reviewed and revised March 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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